Non return valve

[Thuba]

Goodday,
Does a non return valve have a valve flow coefficient? l want to calculate mass flowrate of steam through a non-return valve.
Your assistance will be much appreciated.

 

[GBTorpenhow]

Yes... in one direction.

 

[mk3223]

Typically, you may request the vendor to provide the Cv value of the specific valve on your piping system.
Also, an engineering reference for calculating the Cv of the piping and fittings can be found in the Crane technical paper- Flow of Fluids.

 

[Thuba]

ok

Typically, you may request the vendor to provide the Cv value of the specific valve on your piping system.
Also, an engineering reference for calculating the Cv of the piping and fittings can be found in the Crane technical paper- Flow of Fluids.

ok thank you, maybe my question is a non return valve acts like a ball valve or it doesn't offer significant resistance to flow, hence it wont have the CV value, as it will be fully open?

 

[mk3223]

The Cv values of the ball valves may be different for the full port type from the reduced port. Yes, the flow resistance of the full open ball valve may be insignificant in the piping system, but the Cv of the full port ball valve is to be smaller than the reduced port valve.

 

[GBTorpenhow]

maybe my question is a non return valve acts like a ball valve or it doesn't offer significant resistance to flow, hence it wont have the CV value, as it will be fully open?

In general I would start with the assumption that the Cv of a check valve is worth including until shown otherwise. Actual magnitude of Cv compared to a FP ball valve will depend on the type of check valve, but they can be significantly restrictive.

Everything has a Cv (even straight pipe) the question is whether the Cv is high enough to disregard, or not.

 

[LittleInch]

Depends on the type of non return valve and to a certain extent the velocity through the valve, but the CV can be considerable.

Anything which is spring loaded or has a weight / flapper which lifts out of the way can create quite a lot of DP.

The best ones are lightly spring loaded butterfly valves, especially those inserted between flanges.

 

[Snickster]

Check valves have a very high equivalent length of pipe and pressure drop. It is lowest when the velocity is above a certain value to render the flapper fully opened and below this velocity the flapper is partially opened and pressure drop greater.

The below is from Cameron Hydraulic Data Book, you can get a copy of the book here - it is a very good piping design reference:

Amazon.com : cameron hydraulic data book